Automatic fingerprint scanners are commonly used to obtain an analog or digital image for security, access, verification, or record-keeping applications. In most conventional scanners, a two-dimensional (2D) image of the fingerprint is captured by an imaging device having a matrix of picture elements or pixels arranged as multiple rows and columns. A 2D light-sensitive electronic sensor, such as a charge-coupled device (CCD), is typically used to capture a fingerprint image.
Fingerprint imaging systems must determine if the image presented is a real finger or an optical or mechanical reproduction of a fingerprint, to deny access when a reproduction is presented. Such reproductions may be in the form of a fingerprint printed on paper, a fingerprint printed on clear or reflective plastic, or may be in the form of a three-dimensional (3D) model of a fingerprint, such as a rubber stamp. In the extreme case, a finger may be removed from its rightful owner and used with the imaging system without the rightful owner being present.